An adaptation scheme for quick response to fluctuations in IEEE 802.11 link quality

We propose in this paper a cross-layer link adaptation (CLLA) scheme that uses the number of successful transmissions, the number of transmission failures, and the channel information from the physical layer to determine proper transmission parameters for subsequent medium accesses. In order to improve the throughput of a wireless local area network, dynamic link adaptation schemes can be applied so that the signal and protocol parameters can be adjusted as the radio link conditions change, according to the quality of a wireless channel. Receiver´s signal-to-noise ratio (SNR) and received signal level (RSL) are two critical performance parameters that vary with time due to path loss, shadowing effect, multi-path fading and interference. Hence, according to the SNR and RSL of the latest received frame, a link adaptation scheme can quickly respond to the channel variation and suitably adjust parameters for transmissions. The CLLA scheme lets frames be transmitted at the highest available data rate using proper medium access methods to achieve high throughput. Simulation results show that the CLLA scheme performs well in throughput in practical mobile environments.